Introduction to Reservoir Engineering - Petroleum · PDF fileHistory of Reservoir Engineering

Formation Evaluation and the Analysis of Reservoir Performance Tom BLASINGAME | [email protected] | Texas A&M U.

T.A. Blasingame, Texas A&M U.Department of Petroleum Engineering

Texas A&M UniversityCollege Station, TX 77843-3116

+1.979.845.2292 — [email protected]

Formation Evaluation and the Analysis of Reservoir Performance

Introduction to Reservoir Engineering

Slide — 1


Reservoir Engineering Overview: (General)●Location of World Oil Resources●Reservoir Structure/Depositional Sequences●Petrophysics: Porosity, Permeability, and Correlations●Rock Properties: Homogeneity/Heterogeneity●Phase Behavior of Reservoir Fluids●Formation Evaluation●Pressure Transient Analysis●Reservoir Modeling

History of Reservoir Engineering:●History of Reservoir Engineering ●Tasks of the Reservoir Engineer●Data Sources●Fundamental Drive Mechanisms●Trapping Mechanisms

Orientation: Reservoir Engineering

Slide — 2


From

:Tho

m, W

.T.:

"Pet

role

um a

nd C

oal -

The

Key

s to

the

Futu

re,"

Oxf

ord

Uni

vers

ity P

ress

, 192

9.

Discussion:●The known deposits of oil and gas in 1920.●Offshore deposits would not have been discovered.●Most deposits were discovered by seeps.

Map showing distribution and relative size of world's oil resources, prepared under direction of U.S. Geological Survey in 1920. The general validity of this prophecy has been amply demonstrated in the past eight years-growth

in the importance of the West Texas region balancing the shrinkage in the estimates of Mexican oil reserves.

Overview: World Oil Resources (Circa 1920)

Slide — 3


From

:Tho

m, W

.T.:

"Pet

role

um a

nd C

oal -

The

Key

s to

the

Futu

re,"

Oxf

ord

Uni

vers

ity P

ress

, 192

9.

Discussion:●Note predictions in red text (all are wrong).●Production analysis came about due to taxation.●Early correlation of ultimate recovery given as "appraisal."

AUSTRALIA AND NEW ZEALANDA moderate production of oil may ultimately beattained in New Zealand, but there is apparently only aremote chance that oil fields of more than localimportance will be found in either Australia or NewZealand. Some 60,000 barrels of oil have beenproduced in New Zealand, and seepages have beennoted in as yet untested localities. Small quantities ofoil and gas found at various localities in southeasternAustralia appear to indicate that with further drillingand with more detailed structural mapping inAustralian areas oil fields will be found. No majorproduction is, however, probable.

AFRICAAfrica is quite certainly devoid of major oil deposits,the surface of much of the continent being covered byrocks definitely barren of oil. Such oil production as isnow obtained in Africa (1,100,000 barrels annually)comes almost entirely from the Egyptian fields on theRed Sea coast opposite the Sinai Peninsula, a tinyamount also being produced in Algeria. Some oilmanifestations occur in British and Italian Somali-land, south of the Gulf of Aden; in Madagascar;doubtfully in Portuguese East Africa; in Natal; inAngola; and at various localities around the shore ofthe Gulf of Guinea; but it appears unlikely thatextensive or other than locally important developmentis probable in any of these regions. Fr

om:M

anua

l for

the

Oil

and

Gas

Indu

stry

," U

S In

tern

al

Rev

enue

Ser

vice

—Tr

easu

ry D

epar

tmen

t, 19

19.

Appraisal curve for an Oklahoma oil field.

Production decline curve, showing theextended curve of probable future production.

Overview: World Oil Resources (Circa 1920)

Slide — 4


Diagram of major depositional environments for sandstones.

From

:Ber

g, R

.R.,

1986

, Res

ervo

ir Sa

ndst

ones

: Eng

lew

ood

Clif

fs, N

J, P

rent

ice-

Hal

l.

Discussion:●Schematic for sandstone (clastic) reservoirs.●Transport mechanism is water.●Extremely large deposits of basin sandstones can exist.

Slide — 5

Overview: Reservoir Structure/Depositional Environments


Common sequences of sedimentary structures, texture,and composition observed in reservoir sandstones of

different origins. Diagrams have no vertical scale becausethickness is not a criterion.Fr

om:B

erg,

R.R

., 19

86, R

eser

voir

Sand

ston

es: E

ngle

woo

d C

liffs

, NJ,

Pre

ntic

e-H

all.

Discussion:●Diagrams of sedimentary structures. (on left)● Important to observe/describe core (rock) samples.●Well log responses indicate similar profiles. (on right)

Typical response of spontaneous potential (SP) and gamma-ray (GR)log in sandstone sequences. Log patterns are similar to textural

changes. Dotted patterns indicate dominant sandstone as interpretedfrom the logs. Resistivity (R) or porosity logs are also shown.

Slide — 6

Overview: Common Depositional Structures


Diagrams of systematic packings of uniform spheres as describedby Graton and Fraser (1935). Porosity (n) is given for the principal packings.

From

:Ber

g, R

.R.,

1986

, Res

ervo

ir Sa

ndst

ones

: Eng

lew

ood

Clif

fs, N

J, P

rent

ice-

Hal

l.

Discussion:●Idealized configurations help to establish limits.●Orthorhombic (cubic) is highest (39.5 percent).●Rhombohedral is lowest (26 percent).

Diagrams of unit cells and unitvoids for cubic and rhombohedral

packings of uniform spheres.

Slide — 7

Overview: Concept of Porosity (packings of spheres)


From

:Bea

rd, D

. C. a

nd W

eyl,

P. K

.: “I

nflu

ence

of T

extu

re o

n Po

rosi

ty a

nd P

erm

eabi

lity

of U

ncon

solid

ated

San

d,”

AA

PG B

ull.,

Vol

. 57,

No.

2, (

1973

), 34

9-36

9.

Discussion:●Porosity has many control factors.●Most controls on porosity are from primary deposition.●Secondary (digenetic) processes can also dominate.

Data of Beard and Weyl: (unconsolidated sands) (porosity is given in fraction)Size_______________________

Coarse Medium Fine Very Fine__ Sorting Upper Lower Upper Lower Upper Lower Upper LowerExtremely well sorted 0.431 0.428 0.417 0.413 0.413 0.435 0.423 0.430Very well sorted 0.408 0.415 0.402 0.402 0.398 0.408 0.412 0.418Well sorted 0.380 0.384 0.381 0.388 0.391 0.397 0.402 0.398Moderately sorted 0.324 0.333 0.342 0.349 0.339 0.343 0.356 0.331Poorly sorted 0.271 0.298 0.315 0.313 0.304 0.310 0.305 0.342Very poorly sorted 0.286 0.252 0.258 0.234 0.285 0.290 0.301 0.326

Porosity = f(Grain size,Sorting,Texture,Angularity,Composition (lithology),digenetic processes, andin-situ stress)

For packings of uniform spheres:— Cubic (orthorhombic) = 40% (or 0.40)— Rhombohedral = 26% (or 0.26)

Slide — 8

Overview: Concept of Porosity (unconsolidated sands)


From

:H

ubbe

rt, M

. Kin

g: E

ntra

pmen

t of P

etro

leum

und

er

Hyd

rody

nam

ic C

ondi

tions

, Bul

l. A

m. A

ssoc

. Pet

rol.

Geo

logi

sts,

Aug

ust,

1953

, p. 1

954.

Discussion:●Darcy's experimental apparatus.●Darcy's flow relation.● Image of Henry Darcy.

Governing Relation:

q = FlowrateA = Flow Area∆h = Head ChangeL = Distance

LhkAq

Image of Henry Darcy.Diagram of Darcy's experiment.

Slide — 9

Overview: Concept of Permeability (Darcy's Experiment)


From

:K

atz,

D. L

., C

orne

ll, R

., K

obay

ashi

, R.,

Poet

tman

n, F

. H.,

Vary

, J. A

., El

enbl

ass,

J. R

., &

Wei

naug

, C. G

.: H

andb

ook

of

Nat

ural

Gas

Eng

inee

ring

(McG

raw

–Hill

, New

Yor

k) (1

959)

.

Discussion:●(Important) The "Darcy" is a defined unit.●Image shows square cross-section (can be generalized).●The dimension of permeability is L2 (i.e., area).

The unit of permeability — a Darcy.

Slide — 10

Overview: Concept of Permeability — Definition of a "Darcy"


From

:Arc

hie,

G. E

. "In

trod

uctio

n to

Pet

roph

ysic

s of

R

eser

voir

Roc

ks,"

Am

. Ass

oc. P

et. G

eol.

Bul

., Vo

l. 34

, N

o. 5

, May

195

0, p

p. 9

43–9

61.

Discussion: Archie Petrophysics Proposals●"Petrophysics map" was put forth in 1950 (left).●Proposed the log(permeability) vs. porosity plot (right).●These were the earliest "petrophysics" tools.

Slide — 11

Overview: Petrophysics Map — Archie (1950)


Discussion:● log(permeability) vs. irreducible water saturation (left).●Univariate correlations may not be sufficient.●Multivariate correlations relied on simple relations (right).

Slide — 12

Overview: Petrophysics — Early Correlation Concepts


Physical properties of hydrocarbons and associated compounds.

Correlation: Pseudoreduced Temperature and Pressure for Natural Gases.

Correlation: z-factor for Natural Gases.

Correlation: Viscosity of Natural Gases.

From

:SPE

Mon

ogra

ph S

erie

s 5

—Ea

rloug

her J

ar, R

. C.A

dvan

ces

in W

ell T

est A

naly

sis:

Soci

ety

of P

etro

leum

Eng

inee

rs 1

977.

Slide — 13

Overview: Phase Behavior (Example Gas Data/Correlations)


From

:Eile

rts,

C.K

.: Ph

ase

Rel

atio

ns o

f Gas

Con

dens

ate

Flui

ds,

Vol.

I, M

onog

raph

10,

Bur

eau

of M

ines

, Am

eric

an G

as

Ass

ocia

tion

(195

9) 7

63-7

64.

Phase relationships and compressibility of a single component — propane.

Slide — 14

Overview: Phase Behavior (Vapor-Liquid Equilibria)


First well log — run by Schlumberger brothers (1927).

● Resistivity Logs:— Measures resistance of flow of electric current.— Response is a function of porosity & pore fluid in rock.— Frequently used to identify lithology.

● Spontaneous Potential (SP) Logs:— Measures electrical current in well.— Due to salinity contrast (formation water/borehole mud).— Indicates bed boundaries of sands & shales.

●Gamma Ray Logs:— Records radioactivity of a formation.— Shales have high levels of radioactive minerals.— Gamma ray logs infer grain size/sedimentary structure.

● Neutron Logs:— Counts quantity of hydrogen present.— Used to estimate porosity.— Lithology indicator when used with the density log.

● Density Logs:— Measures bulk density of the formation.— Used to estimate porosity.— Used with sonic log to yield synthetic seismic traces.

● Sonic (acoustic) Logs:— Measures of speed of sound in formation.— Used to estimate porosity.— Used with density log to yield synthetic seismic traces.

Slide — 15

Overview: Formation Evaluation (Types and Uses of Well Logs)


Discussion:●Archie's First Law [Formation Factor = f(Porosity)].●The "cementation factor" (m) is the correlating parameter.●Typical range: 1.7 < m < 2.4.

From

:Kee

lan,

D.:

"Spe

cial

Cor

e A

naly

sis,

" C

ore

Labo

rato

ries

Rep

ort (

1982

).

mwo aRR

F

Slide — 16

Overview: Formation Evaluation — Formation Factor ()


From

:Kee

lan,

D.:

"Spe

cial

Cor

e A

naly

sis,

" C

ore

Labo

rato

ries

Rep

ort (

1982

).

nw

ot SRR

I

Discussion:●Archie's Second Law [Resistivity Index = f(Saturation)].●The "saturation exponent" (n) is the correlating parameter.●Typical range: 1.6 < m < 2.2.

Slide — 17

Overview: Formation Evaluation — Formation Factor (Sw)


What is Pressure Transient Analysis? (or "Well Test Analysis")● The goal of well testing is to collect information about flow conditions in the

well, around the immediate vicinity of the well, as well as in the virgin portionsof the reservoir not influenced by the drilling operations and simulationtreatments, and to obtain informa-tion about the boundaries of the reservoir.The well flowrate is varied and the resulting pressure transients aremeasured. The measurement of variation of pressure with time provides apressure transient data which then can be analyzed to determine the forma-tion parameters that characterize the flow conditions that exist in the system.

●Well test analysis can be considered as a systems analysis technique:

● The system "S" represents the wellbore and the formation that it is incommunication with. The input "I" represents the constant withdrawal of thereservoir fluid and it can be considered as a forcing function applied to thesystem "S". The response of the system, "O" which represents the change inreservoir pressure is measured during the test.

Slide — 18

Overview: Introduction — Pressure Transient Analysis (PTA)

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)


10-3

10-2

10-1

100

101

102

p D, p

Dd

and

p D d

10-2 10-1 100 101 102 103 104 105

tD/CD

Type Curve Analysis — SPE 12777 (Buildup Case)(Well in an Infinite-Acting Homogeneous Reservoir)

Legend: Radial Flow Type Curve pD Solution pDd Solution pDd Solution

Legend: pD DatapDd DatapDd Data

Reservoir and Fluid Properties:rw = 0.29 ft, h = 107 ft,

ct = 4.2×10-6 psi-1, = 0.25 (fraction)o = 2.5 cp, Bo= 1.06 RB/STB

Production Parameters:qref = 174 STB/D

Match Results and Parameter Estimates:[pD/p]match = 0.018 psi-1, CDe2s= 1010 (dim-less)

[(tD/CD)/t]match= 15 hours-1, k = 10.95 md Cs = 0.0092 bbl/psi, s = 8.13 (dim-less)

pDd = 1

pDd = 1/2

10-3

10-2

10-1

100

101

102

p D, p

Dd

and

p D d

10-2 10-1 100 101 102 103 104 105

tD/CD

Type Curve Analysis — SPE 18160 (Buildup Case)(Well in an Infinite-Acting Dual-Porosity Reservoir (trn)— = 0.237, = 1×10-3)

Legend: = 0.237, = 1×10-3

pD Solution pDd Solution pDd Solution

Legend:pD DatapDd DatapDd Data


ct = 2×10-5 psi-1, = 0.05 (fraction)o = 0.3 cp, Bo= 1.5 RB/STB

Production Parameters:qref = 830 Mscf/D

Match Results and Parameter Estimates:[pD/p]match = 0.09 psi-1, CDe2s= 1 (dim-less)

[(tD/CD)/t]match= 150 hours-1, k = 678 md Cs = 0.0311 bbl/psi, s = -1.93 (dim-less)

= 0.237 (dim-less), = CD× = 0.001(dim-less) = 2.13×10-8(dim-less)

pDd = 1/2

pDd = 1

10-4

10-3

10-2

10-1

100

101

p D, p

Dd

and

p D d

10-3 10-2 10-1 100 101 102 103 104

tDxf/CDxf

Type Curve Analysis — SPE 9975 Well 5 (Buildup Case)(Well with Infinite Conductivity Hydraulic Fractured )

Legend: Infinite Conductivity Fracture pD Solution pDd Solution pDd Solution

Legend: pD DatapDd DatapDd Data


ct = 6.37×10-5 psi-1, = 0.05 (fraction)gi = 0.0297 cp, Bgi= 0.5755 RB/Mscf


Match Results and Parameter Estimates:[pD/p]match = 0.000021 psi-1, CDf= 0.01 (dim-less)

[(tDxf/CDf)/t]match= 0.15 hours-1, k = 0.0253 md CfD = 1000 (dim-less), xf = 279.96 ft

pDd = 1/2

pDd = 1/2

10-3

10-2

10-1

100

101

102

p D, p

Dd

and

p D d

10-3 10-2 10-1 100 101 102 103 104

tDxf/CDf

Type Curve Analysis — SPE 9975 Well 12 (Buildup Case)(Well with Infinite Conductivity Hydraulic Fracture )

Legend:pD DatapDd DatapDd Data

Legend: Infinite Conductivity Fracture pD Solution pDd Solution pDd Solution


ct = 4.64×10-4 psi-1, = 0.057 (fraction)gi = 0.0174 cp, Bgi= 1.2601 RB/Mscf


Match Results and Parameter Estimates:[pD/p]match = 0.0034 psi-1, CDf= 0.1 (dim-less)

[(tDxf/CDf)/t]match= 37 hours-1, k = 0.076 md CfD = 1000 (dim-less), xf = 3.681 ft

pDd = 1 pDd = 1/2

c. Case 3 — Fractured gas well, low fracture conductivity. d. Case 4 — Fractured gas well, high fracture conductivity.

b. Case 2 — Unfractured well, dual porosity reservoir.a. Case 1 — Unfractured well, homogeneous reservoir.

Slide — 19

Overview: PTA — Example Pressure Transient Tests


Basic Simulation Approaches:●Analytical approach — providing an exact solution to an approximate problem.

This approach is utilized in classical well test analysis.●Numerical approach — providing the approximate solution to an exact problem.

This approach attempts to solve the more realistic problem with very limitedassumptions.

Reservoir Characterization:●A reservoir simulator can be used to characterize the reservoir under study using

a process called history-matching in which the reservoir parameters are adjustedor tuned to match the past performance of the reservoir.

Forecasting:●After the simulation model has been adjusted and validated through the history

matching process, the model can then be used to forecast future reservoirperformance.

● The history-matched model allows an engineer to investigate reservoirperformance under various production and operation strategies in order todevelop a well-designed strategy for field development and field operationpractices.

Feasibility Analysis:●Results from the simulation study can then be used to perform cost and revenue

calculations in order to select a feasible production and operation strategy forthe field.

What Questions can a Reservoir Model Answer?

Slide — 20

Overview: Reservoir Modeling — Introduction

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)


Establishing the Objectives of the Study:● The basic information required to establish a reservoir study includes:— Amount and quality of data available (i.e., seismic, logs, well tests, etc.).— Recovery stage of the reservoir.— Additional data that would be needed in order to perform the study.— The time to perform the project.

Checking the Inventory of Data:● The information required to perform a field study comes from different sources

(different in levels and disciplines), it is important to perform an exhaustiveorganization of the data.

Data Analysis:● In order to define whether a data set is appropriate for inclusion in a reservoir

model, the engi-neer must be aware of not only the way the data was measured,but also the physics and the conditions of the measurement itself.

Resolution of Data Conflicts:●When there are two or more sets of data representing the same property, the

simulation engineer must define which measurement represents the actualmechanism in the reservoir more closely. To achieve this resolution, these dataare input into the model and, by means of history matching and soundengineering judgment, a "most likely" case is established.

Availability of The Computational Resources:●When defining the objectives of a reservoir study, one must be aware that the

degree of complexity of the description for a given problem must match theavailable computing power.

Slide — 21

Overview: Reservoir Modeling — Preliminary Work

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)


Parameters to be Specified and Parameters to be Matched:● In general, the data to be specified are the flowrates of the reservoir fluids (e.g.,

oil flowrate for oil reservoirs and gas flowrate for gas reservoirs).● The parameters to be matched during the history-match process depend on the

availability of the historical production data. However, there are two broadcategories — the pressure history and the fluid performance data (e.g.,flowrates, water/oil ratio (WOR), gas/oil ratio (GOR), and water/gas ratio (WGR)).

Additional Tools:●Material balance studies and aquifer influx studies.●Pressure transient analysis, which provides permeability and (kh).●Single-well models, which can be used to study coning (and other phenomena).

Quality of a History Match:● The important issue is that the history-match must be consistent with the

objectives of the study. The purpose of the adjusted model obtained from ahistory match will dictate whether the match is good enough and can be usedto perform the desired task with a good level of confidence.

Rules of Thumb for History Matching Studies:●Adjustment parameters should be the data which are least accurately known.●Adjustments within acceptable ranges defined by the engineers and geologists.●Permeability is the most common parameter used in history-matching.

Slide — 22

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)

Overview: Reservoir Modeling — History Matching


Process Selection:● The feasibility of different production processes can be investigated through

simulation by making a forecast of future reservoir performance under differentproduction schemes.

Operational Parameters:● The purpose of specifying operational parameters is to predict the important

events which may be associated with a given production scheme.●Such parameters include: flowrate, well spacing, operating conditions, etc.

Process Optimization:● The focal point of any study is "how fast" and "how much" can we recover?● The optimal flowrate and ultimate recovery are to be investigated/established.

Validating and Analyzing Results of the Forecasting Study:● The validation process is required to ensure that the results are realistic.●Results should be compared to results obtained/estimated by other means.●A good check is to compare the predicted results to the performance of analog

fields which have comparable rock and fluid properties, similar well patternsand spacing, and similar field operations.

Rules of Thumb for Forecasting Studies:●A base case is required for the comparisons of impact of various development

plans and production strategies.●Once the base case is established, any variety of sensitivity cases can be

designed/performed.

Slide — 23

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)

Overview: Reservoir Modeling — Forecasting


There are Five Basic Steps in the Process of a Simulation Study:●Setting concrete objectives for the study.●Selecting the proper simulation approach.●Preparing the input data.●Planning the computer simulations.●Analyzing the results.

Factors that help Us to Define Appropriate Objectives:●Available data.●The required level of detail.●Available technical support.●Available resources.

Two Types of Objectives:●Fact-finding.●Optimization strategy.

Choosing the Simulation Approach:●Reservoir complexity.●Fluid type.●Scope of the study.

Slide — 24

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)

Overview: Reservoir Modeling — Perspectives


The Porous Medium as a Continuum:

The Fundamental Equations:1.The Continuity Equation describes mass accumulation/transfer in the system.2.The Equation of State describes density as a function of pressure and temperature.3.The Energy Equation describes energy accumulation/transfer in the system.4.The Momentum Equation describes momentum accumulation/transfer in the system.5.The Constitutive Equation describes deformation of the fluid as a result of motion.

The microscopic scrutiny of a porous medium reveals that its local properties may vary widely depending on the vol-ume over which the scrutiny is performed. Instead of a microscopic description, the usual way of approaching a description of a porous media and the fluids within it is to use the continuum approach. Fluid properties and porous medium properties are treated as varying "continually" in space.

Slide — 25

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)

Overview: Reservoir Modeling — General Concepts


Porosity:●Core: Core Scale (High Confidence)●Open-Hole Logs: Reservoir Scale (High Confidence)

Permeability:●Core: Core Scale (High Confidence)●Open-Hole Logs: Reservoir Scale (Low Confidence) ●Pressure Transient Analysis: Reservoir Scale (High Confidence)

Reservoir Pressure:● Formation Wireline Tester: Reservoir Scale (High Confidence)●Pressure Transient Analysis: Reservoir Scale (Medium Confidence)

Initial Saturations:●Core: Core Scale (Medium Confidence)●Open-Hole Logs: Reservoir Scale (High Confidence)●Cased-Hole Logs: Reservoir Scale (Medium Confidence)

End-Point Saturations:●Core: Core Scale (High/Medium Confidence)●Open-Hole Logs: Swir — Reservoir Scale (High Confidence)●Open-Hole Logs: Sor — Reservoir Scale (Medium/Low Confidence)●Cased-Log Logs: Sor — Reservoir Scale (High/Medium Confidence)

Slide — 26

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)

Overview: Reservoir Modeling — Potential Areas of Conflict


Always give more Weight to Data which:●Contain a High Degree of Confidence:—Pressure Transient Permeability versus Well Log Derived Permeability—Unsteady-State versus Steady-State Relative Permeability—Bottom-Hole PVT Samples versus Recombined Separator Samples

●Are Measured at the Appropriate Scale for the Reservoir Model:—Well Log versus Core Data—Pressure Transient Data versus Core Data

●Are Representative of the Processes Occurring in the Reservoir:—Differential (Variable Composition) PVT Data—Flash (Constant Composition) PVT Data— Imbibition (Increasing Wetting Phase Saturation) pc and kr.—Drainage (Decreasing Wetting Phase Saturation) pc and kr.

Best Advice:●Use preliminary versions of the simulation model can be used to screen

conflicting data to determine further course(s) of action.

Slide — 27

From

:Ert

ekin

,T. (

Penn

Sta

te U

.)

Overview: Reservoir Modeling — Resolution of Conflicts


Topics:●History of Reservoir Engineering ●Tasks of the Reservoir Engineer●Data Sources●Fundamental Drive Mechanisms●Trapping Mechanisms

From

: Tow

ler,

Bria

n F.

Fun

dam

enta

l Prin

cipl

es o

f Res

ervo

ir En

gine

erin

g. (

2002

) So

ciet

y of

Pet

role

um E

ngin

eers

, Ric

hard

son

Texa

s.

Slide — 28

History of Reservoir Engineering: Orientation

Formation Evaluation and the Analysis of Reservoir Performance Tom BLASINGAME | [email protected] | Texas A&M U. Slide — 29

History: History of Reservoir Engineering — Timelines

History of Reservoir Engineering: (Towler Ch. 1)●1930's:

— Fancher (Petrophysics)— Muskat (Fluid Flow Solutions)— Schilthuis (Material Balance)

●1940's:— Buckley-Leverett (Fractional Flow)— Tarner (Solution-Gas-Drive)— Purcell-Burdine (pc-k-kr)

●1950's:— Early reservoir simulation— Deliverability testing— Advances in phase behavior— Formation evaluation (well logs)

●1960's:— Reservoir simulation— Pressure transient testing— Fractured reservoirs

●1970's:— Fetkovich (Decline Type Curve Analysis)— Advanced pressure transient testing

●1980's:— Fractured wells (1970s/1980s)— Geostatistics— Production-driven economics

●1990's:— Very intensive reservoir simulation— Integrated reservoir management— Blasingame (Production Analysis)— Heterogeneity (k-distributions)

●2000's:— Software-driven reservoir engineering— Distributed temperature and pressure— Deconvolution of well test data

●2010's:— Very large-scale reservoir simulation— Nanoscale petrophysics— Nanoscale phase behavior— Nanoscale fluid flow

From

: Tow

ler,

Bria

n F.

Fun

dam

enta

l Prin

cipl

es o

f Res

ervo

ir En

gine

erin

g. (

2002

) So

ciet

y of

Pet

role

um E

ngin

eers

, Ric

hard

son

Texa

s.


Tasks of the Reservoir Engineer:●How much oil and gas is originally in place?●What are the drive mechanisms for the reservoir?●What are the trapping mechanisms for the reservoir?●What is the recovery factor by primary depletion?●What will future production rates from the reservoir be?●How can the recovery be increased economically?●What data are needed to answer these questions?

Example Activities:●Estimation of reservoir volume by material-balance.●Evaluation of reservoir drive indices.●Fluid displacement theory for recovery.●Decline-curve models — future production/ultimate recoveries.● Improved/enhanced reservoir recovery (IOR/EOR)●Economic evaluation for primary recovery/IOR/EOR?

Slide — 30

History: Tasks of the Reservoir Engineer

From

: Tow

ler,

Bria

n F.

Fun

dam

enta

l Prin

cipl

es o

f Res

ervo

ir En

gine

erin

g. (

2002

) So

ciet

y of

Pet

role

um E

ngin

eers

, Ric

hard

son

Texa

s.


Data Sources:●Reservoir Properties:—Reservoir porosity—Reservoir thickness—Reservoir permeability—Fluid saturations

●Phase Behavior:—Formation volume factors—Gas-to-oil ratios—Fluid viscosities

●Saturation-Dependent Data:—Capillary pressures—Relative permeability

●Production Data:—Production rates—Surface and bottomhole pressure data—Gas and oil gravities measured as a function of time.

From

: How

Het

erog

enei

ty A

ffect

s O

il R

ecov

ery

—W

eber

(198

6).

From

: Tow

ler,

Bria

n F.

Fun

dam

enta

l Prin

cipl

es o

f Res

ervo

ir En

gine

erin

g. (

2002

) So

ciet

y of

Pet

role

um E

ngin

eers

, Ric

hard

son

Texa

s.

Slide — 31

History: Data Sources/Reservoir Engineering Workflows


Fundamental Drive Mechanisms:● Solution-Gas Drive:— Oil expansion for p > pb.— Oil and gas expansion for p < pb.

● Gas-Cap Drive:— p = pb at the gas-oil-contact (GOC)— Gas cap expansion drives oil.

●Waterdrive:— Aquifer under or aside oil column.— Aquifer movement drives oil.

● Gravity Drive:— Gravity drives segregation of phases.— Efficient/effective, but very slow.

● Compaction Drive:— Weak/deformable rock drives fluid.— "Abnormally pressured gas" reservoirs.

● Imbibition Drive:— Capillary imbibition.— Often requires a cyclic process.

From:Dake, L. P.: The Practice of Reservoir Engineering, Elsevier (1994).

(conceptual) Geological model including faults/fluid contacts.

From

: Tow

ler,

Bria

n F.

Fun

dam

enta

l Prin

cipl

es o

f Res

ervo

ir En

gine

erin

g. (

2002

) So

ciet

y of

Pet

role

um E

ngin

eers

, Ric

hard

son

Texa

s.

Slide — 32

History: Fundamental Drive Mechanisms


Structural Trap Stratigraphic Trap

Fault Trap Hydrodynamic Trap

Slide — 33

From

: Tow

ler,

Bria

n F.

Fun

dam

enta

l Prin

cipl

es o

f Res

ervo

ir En

gine

erin

g. (

2002

) So

ciet

y of

Pet

role

um E

ngin

eers

, Ric

hard

son

Texa

s.

History: Trapping Mechanisms


Structural Trap

Fault Trap

Stratigraphic Trap

From

:Mus

kat,

M.:

The

Flow

of H

omog

eneo

us F

luid

s Th

roug

h Po

rous

M

edia

, McG

raw

-Hill

Boo

k C

ompa

ny, N

ew Y

ork

(194

6).

Extracted text from Muskat:● The question naturally arises

regarding the ultimate loss of oil and gas from the original reservoir. In some cases involving fault zones, such losses are evident.

● Assuming, therefore, that as long as abnormal pressures exist the gas accumulations are slowly expelled through the overburden, such leakage must stop when the reservoir pressure is in equilibrium with that in its surroundings.

● Obviously, variations from this condition will exist if over a consider-able area the overlying cover is truly impermeable. Likewise, if rapid subsidence or uplift is in progress and the pressure adjustments are insufficiently rapid to keep pace, abnormally high or low pressures will prevail.

Slide — 34

History: Trapping Mechanisms (Comments from Muskat)


T.A. Blasingame, Texas A&M U.Department of Petroleum Engineering

Texas A&M UniversityCollege Station, TX 77843-3116

+1.979.845.2292 — [email protected]

Introduction to Reservoir Engineering(End of Lecture)

Formation Evaluation and the Analysis of Reservoir Performance

Slide — 35

Introduction to Reservoir Engineering - Petroleum · PDF fileHistory of Reservoir Engineering

Documents